MONTREAL — Senators captain Erik Karlsson remained optimistic, even if he couldn't hide his disappointment after Ottawa lost both games of a home-and-home series against the division-rival Montreal Canadiens.

The Canadiens now lead the Atlantic Division by four points over the Senators, who still have one game in hand.

"It's very upsetting to lose to Montreal two days in a row but they played well and showed they are a quality team," said Karlsson. "They executed really well on the back-to-back and we couldn't do the same."

The Senators (39-24-8) have lost four games in a row now after winning six straight to start the month. Ottawa and Montreal face off once more before the end of the season — next Saturday at the Bell Centre.

"These were fun games to play, even though we were on the losing side," added Karlsson. "We learned a great deal from it. We're going to figure this out. There are no worries.

"Hopefully by next Saturday we have something new to throw at them."

Carey Price was sharp for Montreal (41-23-8) as he stopped 30 shots for his 33rd victory of the season. The home side got goals from Tomas Plekanec, Jordie Benn, Paul Byron and Nathan Beaulieu.

Both Price and Anderson were also between the pipes on Saturday in Ottawa.

With Montreal leading 2-1 in the second on Sunday, Price was at his best when Kyle Turris fired a one-timer destined for the back of the net. The Canadiens goalie sprang to his right and did the splits to get his toe on the puck.

"That's just fun to watch," said Benn of Price's save. "If I did that I'd blow my hamstrings off. He's an amazing goalie. He's there to save us."

Byron put the game to bed in the third period when he went five-hole on Anderson at 3:30 to make it 3-1.

The goal was Byron's 20th of the season. He also added an assist on Montreal's first goal of the game.

"It was pretty special," said Byron. "I didn't think I would be a 20-goal scorer in the NHL. I've come a long way to reach that. It's definitely a special moment. My wife and kids are here in the rink so it's pretty cool for them to see."

Beaulieu made in 4-1, on the power play, scoring with a slapshot from the blue line at 5:08.

Sunday's game had big playoff implications, and the energy on the ice and atmosphere in the stands were definitely playoff-like.

Montreal came out flying, only needing 28 seconds to get the sell-out crowd off its feet.

Plekanec scored his first goal since Jan. 24 when Andrei Markov's shot from the point bounced off Anderson's chest and fell right to the veteran centre in the crease for his eighth of the season.

The lead was short-lived as Pyatt scored the equalizer at 4:36 of the first when his shot from close range deflected off Benn's stick and skipped over Price's outstretched pad.

Benn made up for the mistake later in the same period when his shot from the point took a serious deflection off Viktor Stalberg's stick to beat Anderson glove side at 17:45.

"They (Montreal) came out real strong," said Sens coach Guy Boucher. "They got the goal but we battled right back. But in the second period, I could feel it. Legs were starting to go. The other team was taking over. They 100 per cent deserved the game."